Posted
by
samzenpus
on Wednesday August 04, 2010 @05:53PM
from the giant-balloon-animals-soon-to-come dept.

An anonymous reader writes "More than 100,000 objects bigger than a centimeter wide hover around our planet, accounting for 4 million pounds of junk that befouls our atmosphere and threatens the expensive satellites we actually want in orbit. Dr. Kristen Gates, of Global Aerospace Corporation, proposes that we can clear the skies by attaching a football field-sized balloon to dead satellites, which would increase the orbital drag, eventually bringing a satellite down into the atmosphere where it would burn up. The GOLD — or Gossamer Orbit Lowering Device — unit is easily inflated in space, and best of all, if the deployed GOLD balloon collides with space junk, it won't deflate or break the junk into smaller, less manageable bits."

I find it hard to believe that the mass of a football-field-sized balloon is less than the fuel to just drop the orbit into a brief but colourful brush with the atmosphere.

Well you need to factor in the rocket engine, guidance, and the risk that you may lose active control of the vehicle and be unable to deorbit it. My thinking is that a drag brake (or parachute, solar sail or balloon) could be a separate system. Mostly passive. It gets a simple command, or fires on a timer. It orients itself passively and results in re-entry in a couple of months or so.

If this were air, you'd be completely correct. However, in the vacuum of space and with a very light balloon (we're talking on the order of 10lbs for a football-field size one) there isn't much of a moment arm. The force due to drag would probably be measured in ounces and then you have just the weight of the actual structure. Generally when satellites attitude control systems fail, they don't immediately start spinning like crazy, probably just a few degrees per minute.

Why not simply magnetize the dead satellite or include a small permanent magnet? This would create a magnetic sail. The magnetic field around the satellite would slowly trap plasma from the trace of gases and ions in earth orbit, as well as anything leaking from the sat itself. This would inflate the magnetic field lines and expand a kind of mini magnetosphere around the satellite. This would create drag against the earths magnetic field, and outer atmosphere.

I wonder if you could coat the balloon with a cheap reflective material that would leave residue on debris that impacted the surface. Wouldn't that provide a gradual increase in our tracking ability without costing a whole lot more than the original design?

One way to stop the little stuff would be to put a BIG piece of aerogel in the orbit(s) you want to clean up. As demonstrated by the space probe Stardust which collected many pieces of cometary/inter planetary/interstellar(!) dust grains at relative velocities of tens of km/sec, it is fully capable of decelerating the particles without disintegrating in the process. (Obviously some orbital debris will be much larger so it would be necessary to make the aerogel much thicker than the 1(?) centimeter thickness that was used.) I don't know how thick it was but looking at the space craft diagrams it looks like a waffle in thickness.

The only reason why this is practical is because aerogels are 99% air (or in this case vacuum). Anything else like styrofoam or for that matter wood would be too heavy to put into orbit economically. Unfortunately, since it can't be compressed, this scheme requires one major new breakthrough, the ability to manufacture it in orbit with almost complete recycling of any additional materials needed. From what I understand, one way to make it is to use supercritical liquid CO2 as a solvent. Well, in order to keep your launch costs down, you'll need to recycle almost every last drop of that.

So perhaps giant panels (spheres?) hundreds of meters (kilometers?) across of aerogels could be used to "sponge" up various orbits. You'll probably need to attach a small ion engine to overcome drag (from the atmosphere and from the junk) as well as to move (slowly) to new orbits of interest (and eventually to de-orbit the whole thing or crash it on the moon!).

I no longer login because I feel that while attacking a company's products is fair game (specifically Apple), having stories singling out their users as "selfish" and unkind is not "news for nerds stuff that matters". Am I an Apple fanboi? Let's just say I've used NIX for decades (yes I'm old) and I'm not talking OS X.

IMHO the GOLD balloon should have a dead-man's timer on it. If the balloon hasn't been told _not_ to deploy for over $TIMEOUT days, it should automatically deploy. This would prevent sats that are zapped by CMEs or suffer other comms losses from not deploying their reentry mechanism.